In North America, and indeed in most of the civilized and populated areas of the world, roads have become an integral part of cities, towns, suburbs, and so on. Indeed, most towns and cities contain hundreds or thousands of miles of roads within their boundaries, and also driveways or parking lots for virtually every building within a city or town.
The conventional way and indeed the most popular way to provide roads, driveways, and parking lots with a top surface is to use asphalt for the top surface. A best estimate is that several million miles of roads and several million acres of parking lots within North America are surfaced with asphalt.
However, there are two fundamental problems with asphalt. One problem is that asphalt is oil based, or at least largely so, and therefore a raw material that is in limited supply is being used when it could be being used for other purposes. Secondly, there is a question of durability, which is now generally recognized as a very significant problem. Many existing roadways and parking lots, even very new ones, are degraded considerably largely due to broken asphalt, and cracks or potholes can be found at any given time. The amount of asphalt roadway in North America that has asphalt damage is quite extensive. Most of the damage is caused by weather cycles, which cause expansion and contraction of the asphalt. Any roadway that does not have asphalt damage has most likely been constructed or repaired in the last few years. This is generally unsightly and also quite expensive. Further, oil and other fluids that drip from vehicles while the vehicle is parked or in motion also cause a significant problem. The amount of damage that is done by oil and other fluids from vehicles is considerable. This damage can be seen in virtually every parking lot, driveway, and roadway intersection in North America. Not only does the oil, or whatever fluid that might be leaking from a vehicle, leave a very unsightly stain on the asphalt surface of a roadway, parking lot or driveway, the asphalt surface in time will start to degrade to a point where it is crumbling and needs to be replaced.
While it is possible to replace small portions of the asphalt surface, at least in most cases, this leaves an unsightly patch--or indeed several patches--of new asphalt.
One alternative that has been recently fairly widely accepted in North America as an alternative for resurfacing driveways and small parking lots is interlocking blocks. Interlocking blocks are made of a cementitious or a cement based material having a small relatively constant sized aggregate therein. These blocks come in various shapes and sizes. Basically, these blocks interfit with one another such that the blocks can be installed on a surface to completely cover the surface. The blocks may need to be cut around the perimeter of a surface in order to fit exactly to the outline of the surface. Among the advantages of interlocking blocks are that they do not require the same heavy equipment to install as it takes to create a surface of asphalt, they are easy to replace, only the damaged blocks need replacing which can be done relatively quickly and inexpensively, and they last much longer than an asphalt surface and are much more resistant to damage--including weathering, impact, and leaking oil. They are, however, more expensive to install initially than an asphalt surface, although the cost factor can be spread over many more years since interlocking blocks are much more durable than asphalt. Further, it generally takes longer to install a given area of interlocking blocks than to pave the same area with asphalt, which adds to the initial cost. Largely because of the lower initial cost, many parking lots and driveways are still paved with asphalt instead of surfaces with interlocking blocks. However, because of the long term cost benefits, it is becoming more and more acceptable to use interlocking blocks even where cost is an important and an accountable factor, such as in municipal roads and parking lots or shopping mall and office complex parking lots.
Another advantage of interlocking blocks is that they can, in most cases, allow for ground movement without breaking. The blocks merely shift slightly with respect to one another or in some cases separate slightly from one another, which is usually acceptable. Further, moisture can pass between interlocking blocks which means that normal water seepage into the ground is not interfered with significantly.
Another problem with the present interlocking blocks is that they are concrete based and therefore somewhat porous. This means that they can absorb water which tends to cause them to crack or break during the winter.